How to Make It
Cut potato into 8 (1/2-inch-thick) wedges. Combine potato wedges, 1 1/2 teaspoons cumin, and 1/4 teaspoon salt in a bowl; toss to coat. Heat 1 tablespoon of the oil in a large nonstick skillet over medium-high; add potatoes. Cook, turning often, until potatoes begin to brown, about 5 minutes. Reduce heat to medium; cook until potatoes are golden brown, about 15 minutes. Add onion; cook, stirring occasionally, 4 minutes. Remove from heat; keep warm.
Meanwhile, heat a medium cast-iron skillet over medium-high. Add tomatillos and jalapeño; cook until charred on all sides, about 8 minutes. Remove from heat. Combine tomatillos, jalapeño, pico de gallo, 2 teaspoons lime juice, and 1/4 teaspoon salt in the bowl of a mini food processor. Process until finely chopped, about 1 minute.
Heat remaining 1 tablespoon oil in cast-iron skillet over medium-high. Season both sides of steak with coriander, remaining 1/4 teaspoon salt, and remaining 1 1/2 teaspoons cumin. Add steak to skillet; cook to desired degree of doneness, 4 to 5 minutes per side for medium-rare. Remove to a cutting board; let stand 5 minutes.
While steak rests, toss cooked potato wedges and onions in a large bowl with cilantro, queso fresco, and remaining 1 teaspoon lime juice. Cut steak against the grain into thin slices; drizzle with the tomatillo sauce. Serve steak and sauce with potato mixture.